In a typical deinking process, waste newsprint is introduced into an aqueous bath, which may or may not be alkaline, to which has been added, as a deinking agent, a surface active agent or detergent. The waste newsprint becomes defibered in the bath, and the ink is removed from the fibers by the detergent. The resulting slurry is composed of substantially deinked newsprint fibers, water, and the detergent and ink particles. The slurry is rinsed, liquid is drained from the slurry, and the resulting thickened pulp is recycled into sheets of paper by conventional processing procedures well known to those skilled in the papermaking art.
The effectiveness of the deinking agent is determined by the brightness of the resulting paper sheets. Brightness is determined by a conventional test, and is expressed as a brightness number. The higher the number, the better the brightness.